Digital printing process

Abstract

Embodiments of the invention relate to a method of indirect printing with an aqueous ink. Related apparatus, systems and treatment formulations are disclosed herein. Some embodiments relate to an aqueous treatment formulation for use with an intermediate transfer member of a printing system. In some embodiments, the system comprises a treatment station disposed downstream of the impression station and upstream of the image forming station for forming a uniform thin layer of a liquid treatment formulation onto a surface of an intermediate transfer member (ITM) at a lower run thereof.

What is claimed is: 
     
       1. A method of operating components of a system comprising an intermediate transfer member (ITM), a cleaning station, and a turret assembly disposed downstream of the cleaning station, the ITM comprising a flexible endless belt mounted over a plurality of guide rollers, the turret assembly comprising a turret and a plurality of turret-mounted deflector-objects mounted around a circumference of the turret, the method comprising:
 at the cleaning station, employing a brush disposed outside of a belt-loop defined by the endless belt to remove material disposed on an outer surface of the ITM; 
 thinning an in-motion layer of liquid that is applied, to the outer surface of the ITM, downstream of the brush, wherein the thinning is performed by a given turret-mounted deflector-object of the plurality of turret-mounted deflector-objects of the turret assembly such that: (i) the given turret-mounted deflector-object is disposed outside of the belt-loop and (ii) the given turret-mounted deflector-object faces the outer surface of the ITM to deflect, from the outer surface of the ITM, excess liquid to thin the in-motion layer of liquid; and 
 rotating the turret of the turret-assembly to perform a replacement-operation to replace the given turret-mounted deflector-object with a replacement turret-mounted deflector-object, wherein during the rotating the given turret-mounted deflector-object does not cease to be functional until the replacement turret-mounted deflector-object commences functioning. 
 
     
     
       2. The method of  claim 1 , wherein the given deflector-object is a doctor blade which, when active to thin the in-motion layer of liquid, is oriented normal to the ITM surface. 
     
     
       3. The method of  claim 1 , wherein when active to thin the in-motion layer of liquid, the given deflector-object is urged towards the ITM surface and/or vice versa. 
     
     
       4. The method of  claim 1 , wherein a treatment-station backing roller is disposed inside the loop defined by the endless belt, and wherein when the given deflector-object is active to deflect liquid from the ITM surface, pressure is applied between (i) the given deflector-object and (ii) the treatment-station backing roller via a section of the ITM which is disposed therebetween. 
     
     
       5. The method of  claim 4  wherein the treatment-station backing roller has a soft outer surface. 
     
     
       6. The method of  claim 1 , wherein a cleaning-station backing roller is disposed inside the loop defined by the endless belt opposite of the brush, and wherein pressure is applied between (i) the cleaning-station backing roller and (ii) the brush via a section of the ITM which is disposed therebetween. 
     
     
       7. The method of  claim 1  wherein an additional brush for deflector-object-cleaning is provided, and wherein in some later stage of the turret rotation cycle after which the given deflector-object has ceased to interact with the ITM surface, the given deflector-object is rotated through a group of bristles of the additional brush to remove deposits from the given deflector-object. 
     
     
       8. The method of  claim 7  wherein the turret rotation cycle is such that further rotation of the given deflector-object after cleaning by the additional brush positions the given deflector-object to again interact with the ITM surface to deflect liquid from the ITM surface. 
     
     
       9. The method of  claim 1 , performed such that when the given deflector-object is active, (A) a liquid-removing-portion thereof faces and is disposed below, a downwards-facing portion of ITM surface; and (B) a downwards-facing portion of the ITM surface is downwardly urged towards the liquid-removing portion of the given deflector-object. 
     
     
       10. The method of  claim 1 , perform such that the given deflector-object is a doctor-blade, and when the given deflector-object is active, a liquid-removing portion of the deflector-object is both vertically-oriented and is disposed below, a surface of a horizontally-oriented section of the ITM and (II) the vertically-oriented liquid-removing portion of the given deflector-object is oriented normal to the horizontally-oriented section of ITM. 
     
     
       11. The system of  claim 1 , wherein the given deflector-object is a doctor blade and wherein the method is performed such that the removing of excess liquid is performed at least in part by the combination of: (i) a tip of a vertically-oriented blade which faces, and is disposed below, a surface of a horizontally-oriented section of the ITM; and (ii) a backing roller which is disposed inside of a closed loop of the endless ITM and which downwardly urges the surface of the horizontally-oriented section of the ITM towards the tip of the vertically-oriented blade. 
     
     
       12. A method of operating components of a system comprising an intermediate transfer member (ITM), a cleaning station, and a turret assembly disposed downstream of the cleaning station, the ITM comprising a flexible endless belt mounted over a plurality of guide rollers, the turret assembly comprising a turret and a plurality of turret-mounted deflector-objects mounted around a circumference of the turret, the method comprising:
 at the cleaning station, employing a first brush to remove material disposed on an outer surface of the ITM, the first brush being disposed outside of a belt-loop defined by the endless belt; 
 thinning an in-motion layer of liquid that is applied, to the outer surface of the ITM, downstream of the first brush, wherein the thinning is performed by a given turret-mounted deflector-object of the plurality of turret-mounted deflector-objects such that (i) the given turret-mounted deflector-object is disposed outside of the belt-loop and (ii) the given turret-mounted deflector-object faces the outer surface of the ITM to deflect, from the outer surface of the ITM, excess liquid to thin the in-motion layer of liquid; 
 rotating the turret of the turret-assembly to perform a replacement-operation to replace the given turret-mounted deflector objection with a replacement turret-mounted deflector-object of the plurality of turret-mounted deflector-objects, 
 subsequently and at a time when the given turret-mounted deflector-object has ceased to interact with the outer surface of the ITM, further rotating the turret of the turret-assembly to cause the given deflector-object to pass through a group of bristles of a second brush to remove deposits from the given deflector-object; and 
 subsequently, further rotating the turret of the turret assembly to position the given deflector-object to again interact with the outer surface of the ITM to again deflect liquid therefrom to thin the in-motion layer of liquid. 
 
     
     
       13. The method of  claim 12  wherein when the given deflector-object is active, (A) a liquid-removing-portion of the given deflector-object faces and is disposed below, a downwards-facing portion of ITM surface; and (B) a downwards-facing portion of the ITM surface is downwardly urged towards the liquid-removing portion of the given deflector-object. 
     
     
       14. The method of  claim 12  wherein when the given deflector-object is active, a liquid-removing portion of the deflector-object is both vertically-oriented and is disposed below, a surface of a horizontally-oriented section of the ITM and (II) the vertically-oriented liquid-removing portion of the given deflector-object is oriented normal to the horizontally-oriented section of ITM. 
     
     
       15. The method of  claim 12 , performed such that the removing of excess liquid is performed at least in part by the combination of: (i) a tip of a vertically-oriented blade which faces, and is disposed below, a surface of a horizontally-oriented section of the ITM; and (ii) a backing roller which is disposed inside of a closed loop of the endless ITM and which downwardly urges the surface of the horizontally-oriented section of the ITM towards the tip of the vertically-oriented blade. 
     
     
       16. A method of operating components of a system comprising an intermediate transfer member (ITM), a cleaning station, and a turret assembly disposed downstream of the cleaning station, the ITM comprising a flexible endless belt mounted over a plurality of guide rollers, the turret assembly comprising a turret and a plurality of turret-mounted deflector-objects mounted around a circumference of the turret, the method comprising:
 at the cleaning station, employing a brush disposed outside of a belt-loop defined by the endless belt to remove material disposed on an outer surface of the ITM; 
 thinning an in-motion layer of liquid that is applied, to the outer surface of the ITM, downstream of the brush, wherein the thinning is performed by a given turret-mounted deflector-object of the plurality of turret-mounted deflector-objects of the turret assembly working in combination with a backing roller such that: (i) the backing roller is disposed inside of the belt-loop and downstream of the brush; (ii) the given turret-mounted deflector-object is disposed outside of the belt-loop to and opposite to the backing roller so that the given turret-mounted deflector-object faces the outer surface of the ITM to deflect, from the outer surface of the ITM, excess liquid to thin the in-motion layer of liquid; and 
 rotating the turret of the turret-assembly to perform a replacement-operation to replace the given turret-mounted deflector-object with a replacement turret-mounted deflector-object, wherein when the given turret-mounted deflector-object is positioned opposite of the backing roller to thin the in-motion layer of liquid, at least one of the following is true:
 (I) the given deflector-object is urged towards the backing roller to press thereon via a portion of the ITM dispose therebetween; and/or 
 (II) the backing roller is urged towards the given deflector object to press thereon via a portion of the ITM dispose therebetween. 
 
 
     
     
       17. A method of operating components of a system comprising an intermediate transfer member (ITM), a cleaning station, and a turret assembly disposed downstream of the cleaning station, the ITM comprising a flexible endless belt mounted over a plurality of guide rollers, the turret assembly comprising a turret and a plurality of turret-mounted deflector-objects mounted around a circumference of the turret, the method comprising:
 applying layer of liquid to an outer surface of the ITM as the ITM rotates so that the applied layer of liquid is in-motion on the outer surface of the ITM; and 
 thinning the in-motion layer of liquid, wherein the thinning is performed by a given turret-mounted deflector-object of the plurality of turret-mounted deflector-objects of the turret assembly such that: (i) the given turret-mounted deflector-object is disposed outside of the belt-loop and (ii) the given turret-mounted deflector-object faces the outer surface of the ITM to deflect, from the outer surface of the ITM, excess liquid to thin the in-motion layer of liquid, wherein the method is performed so that at least one of a first condition, a second condition, and a third condition is true, and wherein:
 I. according to the first condition, the thinning is performed by a given turret-mounted deflector-object of the plurality of turret-mounted deflector-objects of the turret assembly working in combination with a backing roller such that:
 A. the backing roller is disposed inside of the belt-loop and downstream of the brush; 
 B. the given turret-mounted deflector-object is disposed outside of the belt-loop to and opposite to the backing roller so that the given turret-mounted deflector-object faces the outer surface of the ITM to deflect, from the outer surface of the ITM; 
 C. at least one of the following is true:
 i. the given deflector-object is urged towards the backing roller to press thereon via a portion of the ITM dispose therebetween; and/or 
 ii. the backing roller is urged towards the given deflector object to press thereon via a portion of the ITM dispose therebetween; 
 
 
 II. according to the second condition, the method further comprises:
 rotating the turret of the turret-assembly to perform a replacement-operation to replace the given turret-mounted deflector-object with a replacement turret-mounted deflector-object, wherein during the rotating the given turret-mounted deflector-object does not cease to be functional until the replacement turret-mounted deflector-object commences functioning; and 
 
 III. according to the third condition, the method further comprises:
 rotating the turret of the turret-assembly to perform a replacement-operation to replace the given turret-mounted deflector objection with a replacement turret-mounted deflector-object of the plurality of turret-mounted deflector-objects, 
 subsequently and at a time when the given turret-mounted deflector-object has ceased to interact with the outer surface of the ITM, further rotating the turret of the turret-assembly to cause the given deflector-object to pass through a group of bristles of a brush to remove deposits from the given deflector-object; and 
 subsequently, further rotating the turret of the turret assembly to position the given deflector-object to again interact with the outer surface of the ITM to again deflect liquid therefrom to thin the in-motion layer of liquid. 
 
 
 
     
     
       18. The method of  claim 17  wherein at least the first condition is true. 
     
     
       19. The method of  claim 17  wherein at least the second condition is true. 
     
     
       20. The method of  claim 17  wherein at least the third condition is true.